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Section 5
5-217
5.31.2.9 RPA (Algerian) Seismic Load
Purpose
The purpose of this command is to define and generate static
equivalent seismic loads as per RPA specifications using a static
equivalent approach similar to those outlined by RPA. Depending
on this definition, equivalent lateral loads will be generated in
horizontal direction(s).
Description
The seismic load generator can be used to generate lateral loads in
the X & Z directions for Y up or X & Y for Z up. Y up or Z up is
the vertical axis and the direction of gravity loads (See the SET Z
UP command). All vertical coordinates of the floors above the
base must be positive and the vertical axis must be perpendicular
to the floors.
Methodology
The design base shear is computed in accordance with section
4.2.3 of the RPA 99 code. The primary equation, namely 4-1, as
shown below, is checked.
W
R
A.D.Q
V =
……………………………..Eqn. 4.1 of RPA 99
where
W = total weight on the structure
A = zone coefficient
D = average dynamic amplification factor
R = lateral R factor
Q = structural quality factor
Seismic zone coefficient and parameter values are supplied by the
user through the DEFINE RPA LOAD command.